1,721,035 research outputs found
Model-Independent Periodic Stability Analysis of Wind Turbines
Full text linkIn this work, a new method is proposed for the stability analysis of wind turbines. The method uses input-output time histories obtained by conducting virtual excitation experiments with a suitable wind turbine simulation model. Next, a single-input/single-output periodic reduced model is identified from the recorded response and used for a stability analysis conducted according to the Floquet theory. Since only input-output sequences are used, the approach is model independent in the sense that it is applicable to wind turbine simulation models of arbitrary complexity. The use of the Floquet theory reveals a much richer picture than the one obtained by widespread classical approaches based on the use of the multi-blade coordinate transformation of Coleman. In fact, it is shown here that, for each principal mode computed by the classical approach, there are in reality infinite super-harmonics of varying strength fanning out from the principal one at multiples of the rotor speed. The relative strength of each harmonic in a fan provides for a way of measuring how periodically one specific fan of modes behaves. The notion of super-harmonics allows one to justify the presence of peaks in the response spectra, peaks that cannot be explained by the classical time-invariant analysis. The Campbell diagram, i.e., the plot of system frequencies vs. rotor speed, is in this work enriched by the presence of the super-harmonics, revealing a much more complex pattern of possible resonant conditions with the per-rev excitations than normally assumed
Model-Independent Periodic Stability Analysis of Wind Turbines from Input-Output Data Using a Periodic ARX Reduced Model
No full textEstimation of Wind Turbine Model Properties - Towards the Validation of Comprehensive High-Fidelity Multibody Models
No full textA MIMO periodic ARX identification algorithm for the Floquet stability analysis of wind turbines
Full text linkThe paper presents a new stability analysis approach applicable to wind turbines. At first, a reduced order periodic model is identified from response time histories, and then stability is assessed using Floquet theory. The innovation of the proposed approach is in the ability of the algorithm to simultaneously consider multiple response time histories, for example in the form of measurements recorded both on the rotor and in the stand still system. As each different measurement carries a different informational content on the system, the simultaneous use of all available signals improves the quality and robustness of the analysis
Estimation of Blade Structural Properties from Experimental Data
No full textWind turbine blades often present complex distributions of their stiffness, mass and inertial properties along the span. We propose a method to estimate such physical parameters so as to match given experimental observations. The procedure can be used to understand the nature of possible discrepancies between designed and manufactured blades and to provide updated high fidelity mathematical beam models to be used in aero-elastic simulations. The formulation is based on the constrained optimization of a maximum likelihood cost function and a noisy measurement fusion approach whereby the data of multiple experiments are used simultaneously in a single estimation process. The proposed method is demonstrated first using simulated data and then in the identification of two real small wind turbine blades
A Wake Detector for Wind Farm Control
Full text linkThe paper describes an observer capable of detecting the impingement on a wind turbine rotor of the wake of an upstream machine. The observer estimates the local wind speed and turbulence intensity on the left and right parts of the rotor disk. The estimation is performed based on blade loads measured by strain gages or optical fibers, sensors which are becoming standard equipment on many modern machines. A lower wind speed and higher turbulence intensity on one part of the rotor, possibly in conjunction with other information, can then be used to infer the presence of a wake impinging on the disk. The wake state information is useful for wind plant control strategies, as for example wake deflection by active yawing. In addition, the local wind speed estimates may be used for a rough evaluation of the vertical wind shear
Simultaneous observation of wind shears and misalignments from rotor loads
Full text linkA wind turbine is used in this paper as a sensor to measure the wind conditions at the rotor disk. In fact, as any anisotropy in the wind will lead to a specific signature in the machine response, by inverting a response model one may infer its generating cause, i.e. the wind. Control laws that exploit this knowledge can be used to enhance the performance of a wind turbine or a wind power plant. This idea is used in the present paper to formulate a linear implicit model that relates wind states and rotor loads. Simulations are run in both uniform and turbulent winds, using a high-fidelity aeroservoleastic wind turbine model. Results demonstrate the ability of the proposed observer in detecting the horizontal and vertical wind misalignments, as well as the vertical and horizontal shears
Floquet Stability Analysis of Wind Turbines Using Input-Output Models
No full textIn this work a method is described for the stability analysis of wind turbines. The method uses input-output time histories obtained by suitable excitations of the system. Next, a periodic reduced model is identified from the recorded response, and used for a stability analysis conducted according to Floquet theory. Since only input-output sequences are used, the approach is model-independent in the sense that it is applicable to wind turbine simulation models of arbitrary complexity. The paper describes a formulation capable of handling turbulent disturbances, and verifies its performance with the help of high fidelity numerical simulations
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